Dehydration—Melting Phenomena in Leptynitic Gneisses and the Generation of Leucogranites: a Case Study from the Kerala Khondalite Belt, Southern India

Braun, I.; Raith, M.; Kumar, G. R. Ravindra

doi:10.1093/petrology/37.6.1285

Cited by 86 publications

(35 citation statements)

References 33 publications

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“…The spinel cordierite mineral phase equilibria thermometry, involving the subsequent decompression reaction in which spinel and quartz reacted to produce cordierite, also yields an upper limit of 900°C. Our results from mineral phase equilibria thermometry are in agreement with the P T ranges obtained by Chacko et al (1996), Braun et al (1996), Nandakumar and Harley (2000), and Cenki et al (2002). However most of the reported high temperatures were obtained from geothermometric computations (except Cenki et al, 2002 who also evaluated the data in petrogenetic grid), and most of the estimates (including Cenki et al, 2002) were restricted to the northern part of TGB and Achankovil Shear Zone area.…”

Section: Discussionsupporting

confidence: 92%

“…The data were checked in the An Ab Or solvus diagrams of both Kroll et al (1993) and Fuhrman and Lindsley (1988) and in both cases, the mesoperthites from CHT yield 1000°C at these pressures. Braun et al (1996) in a previous study of leptynites from the TGB also obtained temperatures up to 1000°C from ternary feldspar thermometry. However, they considered such high temperatures to be unrealistic in their rocks, as it would cause melting, although they concluded that the rocks suffered temperatures of the order of 900°C.…”

Section: Reaction Grid and Pressure Temperature Estimationsmentioning

confidence: 96%

“…The TGB has been the focus of various geological, petrological, isotopic and geochronological investigations for nearly two decades (e.g., Srikantappa et al, 1985;Chacko et al, 1987;Santosh, 1987, Santosh et al, 1990Jackson and Santosh, 1992;Raith and Srikantappa, 1993;Harley and Santosh, 1995;Braun et al, 1996;Nandakumar and Harley, 2000;Cenki et al, 2002;Fonarev et al, 2003). Among these, some studies have also proposed the possible high temperature history of the terrane (e.g., Braun et al, 1996;Chacko et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

“…Among these, some studies have also proposed the possible high temperature history of the terrane (e.g., Braun et al, 1996;Chacko et al, 1996). Several interesting petrological features are preserved in this terrain, including the patchy development of orthopyroxene bearing anhydrous zones within garnet biotite gneisses, termed as "incipient charnockites" that are correlated to the influx of CO 2 rich fluids which desiccated the gneisses along structurally controlled zones and stabilized granulite facies assemblages (e.g., Santosh et al, 1990;Raith and Srikantappa, 1993).…”

Section: Introductionmentioning

confidence: 99%

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Spinel+Quartz association from the Kerala khondalites, southern India: evidence for ultrahigh-temperature metamorphism

Morimoto

Santosh

Tsunogae

et al. 2004

Journal of Mineralogical and Petrological Sciences

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Granulite facies metapelites (khondalites) from Chittikara are characterized by the assemblage Grt + Sil + Bt + Crd + Spl + Kfs + Pl + Qtz ± graphite. The rocks show a series of mineral reactions such as: (1) Bt + Sil + Qtz = Grt + Crd ± Kfs, (2) Grt + Sil + Qtz = Crd, (3) Grt + Crd + Sil = Spl + Qtz , (4) Spl + Qtz = Crd, and (5) Grt + Sil = Spl + Crd. Spinel and quartz occur in direct grain contact and their stability considerations in appropriate reaction grids indicate > 950°C at 8 kbar. This, together with the ca. 1000°C temperatures derived from mesoperthites suggests ultrahigh temperature metamorphism in the khondalite belt. Electron microprobe data on the various minerals have been used to compute pressure temperature estimates from mineral phase equilibria thermobaromtery. Temperature estimates from spinel cordierite thermometry are around 900°C, while garnet cordierite thermometer yields an upper estimate of 818°C. Estimates based on garnet sillimanite plagioclase quartz barometer indicate pressures up to 8 kbar. Evaluation of the microstructures and reactions in the khondalites using available reaction grids for pelitic rocks provide evidence for peak metamorphism at high or ultrahigh temperatures followed by steep decompression from around 8 kbar down to 4 kbar. The P T path attests to a rapid exhumation history probably associated with the extensional collapse following collision of continental blocks during the assembly of Gondwana in the late Pan African.

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Section: Discussionsupporting

confidence: 92%

Section: Reaction Grid and Pressure Temperature Estimationsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Spinel+Quartz association from the Kerala khondalites, southern India: evidence for ultrahigh-temperature metamorphism

Morimoto

Santosh

Tsunogae

et al. 2004

Journal of Mineralogical and Petrological Sciences

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“…The central part of KKB, around Trivandrum, recorded a peak metamorphic condition of approximately 4.8 -5.7 kbar and 830 -860 °C (garnet + sillimanite + cordierite + quartz; e.g., Nandakumar and Harley, 2000) followed by a nearly isothermal decompression (e.g., Santosh, 1987). The presence of abundant and extensive migmatitic gneisses suggests that the peak metamorphic event involved widespread partial melting (Braun et al, 1996, and references therein). Kato et al (2010) recently proposed a typical "clockwise" P -T path for the pelitic granulites, which is based on the crystallization sequence of kyanite (early relict inclusions in cordierite), followed by sillimanite (ubiquitous), and then by andalusite (rare, texturally late).…”

Section: Geological Setting Of the Kerala Khondalite Beltmentioning

confidence: 99%

Metastable corundum + quartz + andalusite association in pelitic granulite from the Kerala Khondalite Belt, southern India

Kato

Hiroi

Harlov

et al. 2011

Journal of Mineralogical and Petrological Sciences

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Corundum in direct contact with quartz and associated with andalusite has been found as an inclusion in alkali feldspar obtained from a leucosome, which forms a part of migmatized pelitic granulite from the Kerala Khondalite Belt, southern India. Thermodynamically, corundum + quartz is metastable relative to andalusite. Textural features suggest that it is a rare example of an arrested reaction corundum + quartz → andalusite which may have been triggered off by the introduction of H 2 O -rich fluids along the cracks of the host alkali feldspar during the uplift and cooling of the leucosome. The metastable corundum + quartz association most likely originated during the crystallization of the Al 2 O 3 -rich leucosome melt when early corundum came into contact with later quartz under conditions with a relatively low H 2 O activity.

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Age and tectonic setting of Neoproterozoic gneissic granites in the southern Yili Block (NW China) and implications for the origins of the continental blocks in SW Central Asian Orogenic Belt

et al. 2021

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Several ribbon-like continental fragments with Precambrian basement were wrapped within Palaeozoic accretionary complexes in the southwest Central Asian Orogenic Belt (CAOB). Their origins and tectonic evolution are essential for understanding the accretionary orogeny of the CAOB and crustal growth versus continental reworking in Phanerozoic. The southern Yili Block in NW of China is one of the major continental fragments in SW CAOB. In order to better constrain the tectonic settings of the Precambrian basement of the southern Yili Block, we present new data of field structures, whole-rock geochemical compositions, zircon U-Pb ages and Lu-Hf isotopic ratios of the Neoproterozoic gneissic granites. Ductile deformation characterized by mylonitic foliations and stretching/mineral lineation is commonly recognized in the gneissic granites, which were cross-cut by undeformed granitoids and mafic dykes. The gneissic granites yielded zircon U-Pb ages of 968 ± 5 Ma, 948 ± 8 Ma, and 873 ± 9 Ma. These gneissic granites show geochemical features of high potassium, peraluminous, calc-alkaline series, enrichment of Th, K, Rb and depletion of Ba, Nd, Sr. They show zircon ε Hf (t) values from À5.5 to 2.0 and two-stage zircon Hf model ages between 1.7 and 2.1 Ga. These new results indicate that the Neoproterozoic gneissic granites in the southern Yili Block derived from partial melting of metagreywackes that most likely had formed in a continental arc setting. A comparison of stratigraphy, magmatism and detrital zircon ages suggests that the southern Yili Block is similar with the northern Yili Block and Chinese Central Tianshan Block in term of Precambrian basement, and these continental fragments might have originated from Neoproterozoic orogenic belts. K E Y W O R D S crustal reworking, Kazakhstan microcontinent, microplate tectonics, Precambrian basement, tectonic evolution, Tianshan (Tien Shan) orogenic belt 1 | INTRODUCTION The Central Asian Orogenic Belt (CAOB) is situated between Baltic-Siberia cratons to the north and Tarim-North China cratons to the south (Figure 1a). It was built by welding of numerous Precambrian microcontinents and Palaeozoic arcs via a series of accretionary com-

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Dehydration—Melting Phenomena in Leptynitic Gneisses and the Generation of Leucogranites: a Case Study from the Kerala Khondalite Belt, Southern India

Cited by 86 publications

References 33 publications

Spinel+Quartz association from the Kerala khondalites, southern India: evidence for ultrahigh-temperature metamorphism

Spinel+Quartz association from the Kerala khondalites, southern India: evidence for ultrahigh-temperature metamorphism

Metastable corundum + quartz + andalusite association in pelitic granulite from the Kerala Khondalite Belt, southern India

Age and tectonic setting of Neoproterozoic gneissic granites in the southern Yili Block (NW China) and implications for the origins of the continental blocks in SW Central Asian Orogenic Belt

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